Submersible well pumps are frequently employed for pumping well fluid from lower pressure oil wells. One type of pump comprises a centrifugal pump that is driven by a submersible electrical motor. The pump has a large number of stages, each stage comprising a diffuser and an impeller. Another type of pump, called progressive cavity pump, rotates a helical rotor within an elastomeric helical stator. In some installations, the motor for driving a progressive cavity pump is an electrical motor assembly attached to a lower end of the pump. Centrifugal pumps are normally used for pumping higher volumes of well fluid than progressive cavity pumps.
Both types of pumps become less efficient when significant amounts of gas from the well fluid flow into the intakes. In a horizontal well, any gas in the well fluid tends to migrate to the upper side of the casing, forming a pocket of free gas. The gas tends to flow into a portion of the intake on the higher side of the pump intake.
Gas restrictors or separators for coupling to the intake of pump in a horizontal well are known in the prior art. While the prior art types may be workable, improvements are desired, particularly for pumps that pump very viscous crude oil.